Retractile conductor cord and method of making such a cord



Jan. 27, 1942. w. T. BARRANS 2,271,057

RETRACTILE CONDUCTOR CORD AND METHOD OF MAKING SUCH A CORD Filed May 12,1939 FIG. FIG. 2

INVENTO/P w T. BA RRA NS ATTOR EV Patented Jan. 27, 1942 RETRACTILECONDUCTOR CORD AND METHOD OF MAKING SUCH A CORD William T. Barrans,Towson, Md., assignor to Western Electric Company, Incorporated, NewYork, N. Y., a corporation of New York Application May 12, 1939, SerialNo. 273,174

3 Claims.

This invention relates to a retractile conductor cord and method ofmaking such a cord, and more particularly to a retractile cord ofhelically coiled form and method of making such a cord.

, In the telephone and other arts it is frequently desirable to connectelectrically operated devices by a compact cord whose length may beextended by a slight tension and returned to a compact form when thetension is released.

Objects of the invention are to provide an effective and efl'icientretractile cord and a method of making such a cord.

In accordance with one embodiment of the invention, a plurality ofconductors are encased in a rubber sheath and vulcanized into a helicalcoil, after which the convolutions of the coil are inverted or reversedto increase the retractility 01' the coil.

A' complete understanding of the invention may be had by reference tothe following description, taken in conjunction with the accompanyingdrawing, in which Fig. 1 is a detail view of a retractile cord with arubber sheath in the form in which it appears immediately aftervulcanization of the sheath; and

Fig. 2 is a similar view of the same cord after the convolutions havebeen reversed.

Referring now more in detail to the drawing, a retractile cord is shownhaving one or more conductors 5 which are encased in a sheath i ofrubber or other suitable material. The rubber sheath 6 may be extrudedupon the conductors in any well-known manner, after which the sheathedconductor is wound upon a mandrel in helical form. It is to beunderstood that the term helical is used in its broadest sense and willrepresent a coil or spiral produced when a strand is wrapped aboutamandrel the transverse cross section of which may be triangular,square, rectangular, circular, oval or a modification of any of these.The rubber sheath of the cord is then vulcanized on the mandrel. When acord thus made is suspended from one end the convolutions tend toseparate due to the weight of the cord. indicating that the initialretractility is not very high. The tendency for the coil to retract intoclosely coiled convolutions can be greatly increased by reversing 'theconvolutions. The greater the spacing between convolutions withinreasonable limits the greater will be the retractility of the cord. Thisinverting of the convolutions may be accomplished by beginning at oneend and inverting each convolution separately. However, a more eflectiveway of reversing the convolutions is by taking a rod 1 in the form of anenlarged needle having an eyelet 8 at one end, projecting it through thecoil, and inserting the ends of the conductors 5 through the eyelet.Then by drawing the needle through the coil all or the convolutions orthe coil may be inverted from right-hand convolutions, as shown in Fig.1, to left-hand oonvolutions, as shown in Fig. 2. If it be desired thatthe final form of the coil have right-hand convolutions, the coil isoriginally made with left-hand convolutions and then inverted. By thismeans 1. A method oi! making a retractile cord which comprises extrudinga continuous unvulcanized rubber sheath on a flexible conducting core,forming the resulting product into helical form. vulcanizing the sheathon the core to form a retractile cord and inverting the helix toincrease the retractility of the cord by drawing one end of the cordthrough the helix.

2. A method of making a retractile cord which comprises applying acontinuous unvulcanized rubber sheath directly on a flexible conductingcore, thereafter forming the resulting product into helical form,vulcanizing'the sheath on the core to form a retractile cord andinverting the helix to increase the retractility oi' the cord by drawingone end 01 the cord through the helix.

3. A method of making a retractile cord which comprises coating aconductor with thermoreactive material, forming the coated cord intoretractile form, setting said thermoreactive material in the form 01' ahelix, and drawing one end 01' the cord through the helix to invert thecord.

WILLIAM T. BARRANS.

